Source of electrical power for an electric vehicle and other purposes, and related methods

ABSTRACT

Microthin sheet technology is disclosed by which superior batteries are constructed which, among other things, accommodate the requirements for high load rapid discharge and recharge, mandated by electric vehicle criteria. The microthin sheet technology has process and article overtones and can be used to form thin electrodes used in batteries of various kinds and types, such as spirally-wound batteries, bipolar batteries, lead acid batteries silver/zinc batteries, and others.  
     Superior high performance battery features include: (a) minimal ionic resistance; (b) minimal electronic resistance; (c) minimal polarization resistance to both charging and discharging; (d) improved current accessibility to active material of the electrodes; (e) a high surface area to volume ratio; (f) high electrode porosity (microporosity); (g) longer life cycle; (h) superior discharge/recharge characteristics; (i) higher capacities (A·hr); and (j) high specific capacitance.

FIELD OF INVENTION

[0001] The present invention relates to electrical batteries in generaland more particular to improved sources of electrical power for anelectric vehicle and other purposes, and related methods.

BACKGROUND

[0002] In its most elemental way, a source of electrical power istypically a battery which may comprise one or more battery cells. Eachcell typically comprises encapsulized electrolyte and positive andnegative electrodes. During cell operation, electrons move through thesolid electrode material, to the electrolyte/electrode interface. There,a faradaic (charge-transfer) reaction occurs, which transfers the chargefrom electrons to electrolyte species. Ions then flow through theelectrolyte to the opposite electrode, where another faradaic reactiontakes place, liberating electrons into the solid electrode material.Electrons then flow from the electrode to the external load connected tothe battery.

[0003] Because of a number of fundamental deficiencies, including butnot limited to ionic resistance and electronic resistance within thecell, prior battery technologies have proven to be unsatisfactory forhigh discharge and high recharge power requirements including thoseimposed in the operation of an all-electric or hybrid electric vehicle.Electric vehicles typically take the form of parallel-configured andseries-configured vehicles.

[0004] Parallel-configurated electric vehicles require a battery packwhich is smaller in size, and yet can be both discharged and rechargedat rates comparable to those specified for the series-configured hybrid.No battery presently available can approach the power requirements(especially charging power) for the parallel-configured hybrid vehicle.

[0005] The limitations in power are not necessarily due to thefundamental electrochemistry of the battery systems, but instead areoften due to certain design constraints of the batteries, particularlythe electrodes. Among the design constraints of prior battery packs forelectric vehicles are:

[0006] excessive solid-phase resistance to electronic current flow;

[0007] excessive electrolyte-phase resistance to flow of ionic currentwithin the electrode; and

[0008] excessive kinetic resistance in the electrode, caused at leastpartially by the nature of electrode surface area.

[0009] Prior spiral lead acid batteries often perform better at highrates than prismatic (parallel-plate) batteries. Still, the performanceof prior spirally-wound lead-acid cells is not adequate for manyload-levelling applications requiring high rate charging anddischarging, such as hybrid electric vehicles.

[0010] Prior silver-zinc batteries each consists of a zinc electrode(the negative), a silver-oxide electrode (the positive), and an alkalineelectrolyte. Each electrode is supported by some conductive grid.Numerous materials have been used, and zinc metal (for the negative) andsilver metal (for the positive) are common. In the fully-charged state,the negative consists of zinc metal (usually porous), and the positiveof AgO (Ag₂O is also used). The discharge reactions involve

Zn-->ZnO

AgO-->Ag₂O-->Ag.

[0011] The open circuit potential of the fully-charged prior cell isaround 1.83 V, depending on the electrolyte (KOH) concentration. Thisbattery is the highest-energy density battery using an aqueouselectrolyte. It is also capable of high power density. Cycle life isshort due to the solubility of both zinc and silver, and the aggressiveaction of silver on separator materials. The cost is obviously high,such that its application is usually limited to military and aerospacepurposes, where energy density is of primary importance, and cost isnot.

[0012] Spiral wound lead acid batteries are known wherein electrodes aremade by applying appropriate pastes to a lead or lead alloy grid, andcuring the paste to form the electrode active materials. Pastes arecomposed of lead oxides, sulfuric acid, and other components. Thecompositions will vary depending on the vendor. Cells are made byplacing separators between the pasted electrodes and rolling theelectrodes and separators into a coil. The separator material is usuallycompressed during cell winding. Consequently, the space betweenelectrodes is conveniently made small, which provides somewhat lowerinternal cell resistance.

[0013] Spaced rectangular flat plate electrodes in lead acid are alsoknown, which are made by the so-called Planté process. This processoriginally involved the simple electrochemical oxidation of lead metalin sulfuric acid. The resultant capacity of the electrodes was low, butgradually increased as the cells were charged and discharged. Theresulting electrodes proved very durable, but suffered from low specificcapacity (A·hr/cm²).

[0014] Later improvements allowed for increased capacity. The first wasthe addition of lead-solubilizing agents² (such as KClO₄, KClO₃, HCl,HNQ, and H₂C₂H₃O₂) to the sulfuric acid formation solution. The use ofthese agents resulted in more rapid and deeper penetration of thecorrosion layer on the flat electrode plates during oxidation leading tohigher specific capacity. The second was the mechanical working of thelead to increase surface area, such as by creating lead ridges on theflat electrode plates. This further increased the electrode capacity.

[0015] During the early part of this century, Planté electrodes weregradually replaced by pasted electrodes for most energy storageapplications, due to the higher specific capacity, and despite theshorter life expectancy. Planté electrodes are still used commerciallyin applications where long life is paramount, especially stationaryapplications (such as stand-by power). A number of manufacturers stillproduce Planté batteries in the 100-2000 A·hr range and the U.S.Department of Defense uses Planté batteries for some stand-by powersupply applications where long life is needed. The principal advantageof Planté batteries is in their stability. It is not uncommon for Plantébatteries to have a useful life of decades.

[0016] The processing of Planté flat plate batteries are typicallycostly and time intensive compared to pasted electrode batteries.Flushing of potassium perchlorate adds significantly to the time andcost requirements.

BRIEF SUMMARY AND OBJECTS OF THE INVENTION

[0017] In brief summary, the present invention overcomes orsubstantially alleviates electrical power source problems of the past inthe field of electrically-driven vehicles and in other fields as well.Microthin sheet technology is provided by which batteries areconstructed which accommodate the requirements for high load rapiddischarge and recharge, mandated by electric vehicle criteria. Theexceptional characteristics of batteries made according to thisinvention accommodate cost-effective use for many other purposes aswell. The microthin sheet technology can be used to form batteries ofvarious kinds and types, such as spirally-wound batteries, bipolarbatteries, lead acid batteries, silver/zinc batteries and others.

[0018] The micro thin sheet technology embraces one or more of certainbasic characteristics, i.e. enhanced power and capacity due to: (1) thethinness of the electrode-forming sheet; (2) the high degree of active(corroded) material created on the sheet; (3) the presence ofundulations, corrugations, or up and down irregularities in the sheet;(4) the spiral orientation of positive and negative separated thin sheetelectrodes; (5) the combination of the thin sheet technology to bipolarbattery technology; (6) implementation of microcorrugations ormicro-irregularities in a thin sheet of foil; (7) the creation of agreater amount and greater depth of active material on a thin sheetelectrode; (8) provision of electrochemically-caused high microporosityin a thin sheet electrode; (9) facilitating a high degree of electrolyteaccessibility to electrodes; (10) elimination of the need to and costsassociated with rinsing metal solubilizing agent from pores in thinmetal sheets for use as battery electrodes; (11) concurrent and conjointformation of positive and negative electrodes; (12) use of thin sheetelectrode-to-tab-to-terminal technology; and (13) thin sheet bipolarbattery technology.

[0019] Superior high performance battery features are achieved by thepresent invention due to one or more of the following: (a) minimal ionicresistance; (b) minimal electronic resistance; (c) minimal polarizationresistance to both charging and discharging; (d) improved currentaccessibility to active material of the electrodes; (e) a high surfacearea to volume ratio (cm²/cm³); (f) high electrode porosity(microporosity); (g) longer life cycle; (h) superior discharge/rechargecharacteristics; (i) higher capacities (A·hr); (j) high specificcapacitance (C/cm²); (k) the microthinness of the electrode sheets; (l)use of a spiral cell array.

[0020] Other advantages are derived from the present invention includingbut not limited to cost-effective manufacturing, use of mass productiontechniques, reduction in time required to manufacture, lower initialcapital outlays, superior quality, modest floor space requirements andease of production.

[0021] With the foregoing in mind it is a primary object to overcome oralleviate past problems in the field of electrical power sources forelectrically-propelled vehicles and in other fields as well.

[0022] It is a further dominant object to provide batteries and methodsof making batteries which comprises the novel thin sheet technology ofthe present invention.

[0023] Another important object is the provision of batteries andmethods of making batteries which accommodate high load rapid dischargeand recharge utilization.

[0024] Still another paramount object is the provision ofspirally-wound, bipolar lead-acid, silver/zinc, and other batterieswhich have superior characteristics due to use of the novel microthinsheet technology of the present invention.

[0025] A further object of value is provision of batteries and methodsof making batteries comprising one or more of the basic characteristicsand/or the features and/or advantages mentioned above.

[0026] Another object of the invention to provide an electrode with thedurability and long life of prior Planté electrodes, but comprised of athin sheet with a higher capacity and lower cost of manufacture ascompared to prior Planté electrodes.

[0027] It is also an object of the invention to provide, in a battery,thin sheet highly corroded electrodes having high and low surfaceirregularities.

[0028] Another object is the provision in a battery of thin sheet,spirally-configurated highly corroded electrodes.

[0029] An object of importance of the invention is to provide thinsheet, highly corroded electrodes in a bipolar battery.

[0030] It is further an object of the invention to provide highlycorroded thin sheet electrodes in spirally-wound lead acid batteries.

[0031] An object of significance is to provide thin sheet corrodedelectrodes having high and low surface irregularities in bipolarlead-acid batteries.

[0032] Yet another object of the invention is to provide thin sheetcorroded electrodes having high and low surface irregularities insilver/zinc batteries.

[0033] A further object of the invention is to provide novel electrodesin bipolar silver/zinc batteries.

[0034] Yet an important object of the invention is to provide novelcorroded electrodes having high and low surface irregularities inspirally-wound silver/zinc batteries.

[0035] Another object of the invention is to provide microthin sheethighly corroded electrodes with enhanced microporosity.

[0036] A further object of the invention is to provide a novel processfor manufacturing silver/zinc batteries.

[0037] A further object of the invention is to provide novel microthinsheet electrodes in spirally-wound batteries.

[0038] Yet another object of the invention is to provide novel microthincorroded sheet electrodes in bipolar batteries.

[0039] Another object of the invention is to provide a process forproviding surface irregularities in corroded lead foil for use inbattery electrodes.

[0040] A further object of the invention is to provide a process for therapid filling of spirally-wound cells that comprise corrugated thinsheet electrodes.

[0041] Yet another object of the invention is to provide spirally-woundlead acid battery with novel thin sheet corroded electrodes.

[0042] Another important object of the invention is to provide in situformation of thin sheet corroded electrodes in spirally-wound cells.

[0043] A further object of the invention is to provide a process for insitu formation of thin sheet electrodes in bipolar cells.

[0044] Yet another object of the invention is to provide a battery witha thin corrugated lead foil electrode with an improved life cycle.

[0045] An object of the invention is also to provide a battery withimproved discharge/recharge properties.

[0046] A further object is to provide novel thin sheet electrodes thatminimize the various resistances in the electrode structure.

[0047] Further objects of the invention will become evident in thedescription below.

BRIEF DESCRIPTION OF THE DRAWINGS

[0048]FIG. 1 is a diagrammatic representation of a series-connectedhybrid electric vehicle;

[0049]FIG. 2 is a diagrammatic representation of a parallel-connectedhybrid electric vehicle;

[0050]FIG. 3 is a flow chart comprising one spiral battery process ofthe present invention with the conventional pasted electrode process;

[0051]FIG. 4 is an expanded flow sheet of a portion of the conventionflat electrodes Planté formation process;

[0052]FIG. 5 is a cross-sectional schematic of a convention prior artPlanté formed bipolar flat plate electrode;

[0053]FIG. 6 is a cross-sectional schematic of a bipolar electrodeformed in accordance with principles of the invention;

[0054]FIG. 7 is a cross-sectional schematic of a conventional slottedprior art Planté formed flat lead plate electrode;

[0055]FIG. 8 is a cross-sectional schematic of a lead blank having manmade high and low irregularities from which an electrode according tothe present invention may be formed;

[0056]FIG. 9 is a cross-sectional schematic of a conventional prior artPlanté formed flat lead plate electrodes without slots;

[0057]FIG. 10 is a cross-sectional schematic of a thin sheet electrodeformed from blank of FIG. 8 by implementation of principles of thepresent invention;

[0058]FIG. 11 is a three dimensional schematic showing thin sheetpositive and negative electrodes, made in accordance with the presentinvention, and two separator dielectric layers preparatory to spirallywinding the four layers;

[0059]FIG. 12 is a top plan schematic of the four layers of FIG. 11rolled into a tight spiral coil;

[0060]FIG. 13 is a three dimensional schematic showing the coil of FIG.12 placed in a container to form a cell;

[0061]FIG. 14 is a fragmentary three dimensional schematic of a cellformed in accordance with the present invention, showing the thin sheetpositive and negative electrodes respectively equipped with exposed tabextensions;

[0062]FIG. 15 is a fragmentary three dimensional schematic of the cellof FIG. 14 with the positive and negative tabs welded together;

[0063]FIG. 16 is a fragmentary three dimensional schematic of the cellof a battery pack comprising three cells of the type shown in FIG. 15electrically connected in series with monoblack posts or terminalsattached; and

[0064]FIGS. 17 and 18 are a graph showing performance data derived frombatteries produced in accordance with the principles of the presentinvention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

[0065] The present invention is directed towards significantimprovements in batteries by which, among other things, electricvehicles can be satisfactorily operated for a protracted time, withoutencountering debilitating discharge and recharge problems. The presentinvention has a broad range of applications which includes but is notlimited to provision of sources of electrical power for electricvehicles.

[0066] With reference to FIG. 1, an electric vehicle 20 isdiagrammatically illustrated. Vehicle 20 is characterized as being“hybrid” because it contains two power sources, i.e. (1) an internalcombustion engine, comprising part of the auxiliary power unit 22, and(2) an electrical power source, comprising part of the electrical drivetrain 24. Because the unit 22 and drive train 24 are arranged in series,the hybrid electric vehicle (HEV) 20 is called a “series-connectedhybrid electric vehicle.”

[0067] With reference to FIG. 2, an electric vehicle 30 isdiagrammatically illustrated. Vehicle 30 is characterized as being“hybrid” because it contains two power sources, i.e. (1) an internalcombustion engine comprising part of the primary power unit 32 and (2)an electrical power source, comprising part of the electrical power unit34. Because the units 32 and 34 are arranged in parallel, the HEV 30 iscalled a “parallel-connected hybrid electric vehicle.” The electrodes ofthe invention rely on thin sheet technology which surprisingly minimizesthe various resistances heretofore consistently found in the priorelectrodes.

[0068] In traditional prior lead acid electrode technology, batterieshave not been produced having a high rate load-leveling capability, suchas is needed in HEV. Consequently, lead acid batteries heretoforesuffered rapid loss of capacity under such rigorous use. The electrodesof the present invention provide batteries which can operate at veryhigh power levels and for long periods of time. They can be recharged inno more than a few minutes. Principles of the present invention includebut are not necessarily limited to:

[0069] 1. Active material regions of improved depth having minimal ionicresistance, i.e. reduction in the electrolyte-phase resistance to flowof ionic current within the electrode;

[0070] 2. Active material regions of improved depth having minimalelectronic resistance, i.e. reduction in the solid-phase resistance toelectronic current flow;

[0071] 3. The chemical reactions of minimal polarization resistance(during both charging and discharging); and

[0072] 4. Low capacity losses by minimizing morphological changes duringoperation.

[0073] Polarization is the reduction in cell voltage that occurs due toelectrode reactions. It is related to the energy required to drive thereactions. It is reported in volts. Some electrode reactions occur morereadily than others. For example, nickel is a sluggish electrode, suchthat voltage drops of 0.1-0.5V can occur at that electrode when highrate discharges are attempted. By contrast, certain lead oxide or leadelectrodes can be discharged at similar rates and only suffer apolarization of tens of millivolts. Obviously, if high rate operation isto be obtained from a battery, then electrode materials must be usedthat will not have prohibitively large reaction polarization losses.Electrode reactions do not necessarily occur with the same rate oncharge and discharge. Some, for example, are easier to discharge at highrates than to recharge at high rates. The lead dioxide electrode, usedin a lead-acid battery, is an example of such asymmetric reactivecapabilities. It recharges with more difficulty than it discharges.

[0074] The high performance electrodes of thin corroded sheets with highand low surface irregularities according to this invention have beenused in lead acid batteries and found to possess the characteristicsmentioned above. The batteries of the invention comprise microthinelectrode layers within the range of 4-62 mils comprised of a highsurface area within the range of 10,000 to 50,000 cm²/cm³, porositywithin the range of 5-95%, depending on intended application, includingto a far greater depth, and minimal electronic resistance. Sometimesinternal resistance of a battery pack is expressed as “stack impedance.”Stack impedance is mainly due to voltage drops occurring inside ofindividual cells (due to ohmic resistances and chemical reactionresistance) and voltage drops as current flows through various currentcollectors and conductive straps and connections in the battery pack.Restated, the stack impedance is mostly due to the internal cellresistances. The more efficient the cell, the lower the internalresistance. The present invention minimizes these resistances, resultingin a materially lower stack impedance. A modified process, constitutingseveral improvements over the traditional Planté process, has been foundto be a cost-effective and convenient way of making such electrodestructures. The surface irregular microthin electrode sheets have beendeveloped to maximize the specific capacity by increasing the ratio ofactive (corroded) material to support material. Specific electrodecapacities can range from 1-45 C/cm² and higher. “Specific capacity is ameasure of charge (Coulombs or ampere-hours) which can be stored pergiven area of electrode face (cm²). Traditional Planté electrodeshistorically have been thought of as having low specific capacityrelative to the more common pasted electrodes. The present technologyhas resulted in microthin electrodes which have specific capacitycompable to those of pasted electrodes, but with much better high powercapability. Useful life in years is improved.

[0075] The microthin electrode construction begins by forming thesurface irregularities in the thin sheet. This can be done by cuttingparallel grooves in metal foil, by die-stamping a desired high and lowrepeating or random pattern in the microthin sheet or in any othersuitable way. As stated, the thin electrode sheet is within the range of4-62 mils. The height and depth of the high and low surface regions, istypically within the range of 2-20 mils and the width of high and lowirregular surface areas is typically within the range of 2-20 mils.

[0076] When grooves and ridges comprise the high and low surfaceirregularities, center-to-center spacing between consecutive grooves andconsecutive ridges, respectively, may be within the range of 4-40 mils.For lead acid microthin electrodes, lead foil may be used as a startingmaterial for the electrode. A large number of microscopic, parallelgrooves, for example, may be cut into the soft lead foil, usually onboth sides. One way of creating such parallel grooves in a thin smoothsheet is by passing the sheet through a rolling machine, whose rollersare equipped with teeth by which the grooves are formed, much as afarmer can create furrows in a field by discing. Another method whichcan be used is to cast lead into the desired thin corrugated orirregular form using, for example, a conventional continuous caster. Insitu formation is also satisfactory. Other suitable thin electrodeprocesses may be used for lead and other thin electrode metals, such assilver and zinc, to form surface irregularities.

[0077] The electrode is next electrochemically formed from the thinsheet comprising at least one and normally both irregular surfacescomprising high and low regions. Specifically, the thin irregular sheetis electrochemically oxidized by placing the sheet in a chemical bathand subjecting it to current flow. For lead metal, this hasconventionally been done in the past, as depicted in FIG. 10, usingrelatively thick metal plates in a sulfuric acid solution containingpotassium perchlorate as a lead-solubilizing agent. Large grooves, inmillimeters, have sometimes been placed in the thick plates subjected tothe Planté process, as shown in FIG. 7. Conventional thick Plantéelectrodes have active material regions which have an effective usefulthickness of only a few mils. This is due to the fact that the porosityof the active material decreases with thickness. At the front (outside)of the active material region (as shown in FIGS. 7 and 9) porosity isoften above 50%. However, the porosity can be under 10% for very thickPlanté active material regions. Consequently, the underlying activematerial in the thick Planté electrodes is only poorly accessible toelectrolyte, due to the low porosity.

[0078] The present invention relies on microthin sheets and nitric acidin lieu of perchlorate because extensive rinsing is not required, asexplained in greater detail hereinafter. The formation of a porous leaddioxide region results from this process, which can be used as apositive electrode, or by subsequent electrochemical reduction to porouselemental lead, as a negative electrode. The Planté process has beenlimited to creating flat or substantially flat planar and thickelectrodes, not spiral or bipolar electrodes or electrodes which aremicrothin.

[0079] An aspect of the present invention is the use of a novel andimproved battery chemistries to oxidized microthin sheet metalelectrodes, other than lead/lead oxide systems. For other metals, theelectrochemical oxidation is done with current flow in an appropriateelectrolyte (typically acidic or basic), which contains a commerciallyavailable metal-solubilizing agent. After oxidation, the corrosion oractive portions of the thin sheet electrode may be subjected to anelectrochemical reduction in the same or similar agent to convert theactive portions from an oxidized state to the porous elemental metal,where a negative electrode is being formed.

[0080] Another aspect of the invention is the incorporation of thinelectrodes, formed in accordance with the present method, for either oneof both of the electrodes in a cell.

[0081] The present invention has a scope where only one of twoelectrodes in a battery cell is constructed in accordance with thepresent invention. For example, a thin sheet positive electrode formedin accordance with the principles of the present invention could be usedin conjunction with a traditional pasted negative electrode to provide aviable battery.

[0082] As the oxidation proceeds, a surprisingly large porous oxidelayer grows on the irregular metal surfaces of the thin sheet electrode.The depth of the corrosion layer is significant, but depends on theoxidation time, current density, and other factors that are within theability of the practitioner to determine with no more than routineexperimentation. The electrochemical formation continues long enough tocreate an active region of substantially uniform corrosion and ofadequate depth. The depth can be substantial and greater than thedimensions of the underlying untreated metal. Preferably, the width ofthe lead ridges or other high regions is chosen such that while bothsides and the top are corroded, a small portion of unreacted leadremains inside each ridge or high region (under the porous region), andprovides mechanical support. However, the thin sheet may be composite,particularly in bipolar batteries, so that the untreated support regionis formed of a conductive material different from the corroded material.at or near the surface The width of the grooves or low regions issufficient to allow for expansion from formation of porous activematerial along the sides of the ridges and at the bottom of the groovesor low regions. See FIG. 10. In some embodiments the grooves form flowpaths for rapid dissemination of electrolyte. The grooves or low regionsserve, in some configurations, as reservoirs for electrolyte. Thegrooves can also contain gas and/or separator material. In some cases,gas volume can be significant. The capacity is thus increased, due toimproved accessibility of the electrolyte to the active material and tothe current flow.

[0083] Capacity is also improved due to surprisingly high overallporosity in the active regions. The porosity of the active regions oflead acid cell electrodes (porous lead dioxide of porous elemental lead)is naturally-stable and within the range of 5-65% depending upon theintended application. This porosity is best characterized as“microporosity.” With corrugated or irregular thin sheet electrodes, thegrooves or low regions also contribute to the porosity. Porosity iselectrochemically created “pores,” in the high and low irregular surfaceor surfaces of the thin sheet electrode. These micropores can provideeffective stable apparent porosity values of 70 to 80% in someconfigurations of the invention. In some cases, the degree of oxidationof corrugate or otherwise irregular surfaces of the thin sheet can fillor substantially fill the grooves or other low regions, as depicted inFIG. 10.

[0084] A further benefit of the corrugated or surface irregular thinsheet electrodes in a batteries is a very rapid recharge and dischargeability. The entire active material region is highly accessible to bothelectrolyte and electronic current. It has been found that with suchultra thin microporous active material regions full recharge ordischarge can be accomplished in seconds to minutes, depending on avariety of conditions such as discharge rate, depth of discharge, andmethod of charging, compared to hours for known lead acid batteries.

[0085] The level of stored energy available through implementation ofthe present invention is within the range of 0.1 to 200 W·hr (0.05 to100 A·hr) per battery cell.

[0086] A common metric for discharge and recharge is the “C Rate.” The Crate is the rate at which the total capacity of a battery is removed orrestored. A 1C rate is a one hour rate (i.e. a complete discharge orrecharge in one hour). A C/20 rate is a complete discharge or rechargein 20 hours. Similarly, a 20C rate is a complete discharge or rechargein {fraction (1/20)} hour, or 3 minutes. Prior batteries are typicallyrecharged or discharged at rates equal or slower than a 1C rate. Priorto the present invention, a rapid recharge was considered to occur at arate greater than 1C. High rate discharges are usually 10C or greaterwith prior battery configurations. Spiral batteries according to thepresent invention have been recharged at 100C-200C rates. Dischargeshave been performed at up to 450C.

[0087] The corrugated or surface irregular thin sheet electrodes areassembled into a battery structure using conventional techniques, afterelectrochemical formation is completed. A bipolar battery may beconstructed within the scope of the present invention by formingirregular high and low regions on thin flat sheets and electrochemicallytreating the sheets as explained above to form corroded regions. Oneside of the sheet is then reduced to a porous metal state. The platesare then assembled into a bipolar stack using conventional bipolartechniques. See FIG. 6.

[0088] A spirally-wound lead acid battery, using thin sheet electrodesof the present invention, is made by winding or otherwisespirally-configurated the thin sheet positive and negative electrodesseparated by layers of dielectric material, called separators. Strips oflead foil may be corrugated or given irregularities comprising high andlow surface regions and electrochemically treated as described. The thinelectrodes are then wound into a cell roll which is inserted into acylindrical container. See FIGS. 11 through 13. Tabs are cut before orafter winding and placement in the container so as to extend upward atthe top of the coil (above the active region of the electrodes). SeeFIG. 14. Electrolyte is added. The positive and negative tabs arerespectively welded together by molten lead which become terminals ofthe cell. See FIG. 15.

[0089] Winding of electrodes is broadly known. See U.S. Pat. Nos.4,158,300; 4,709,472; 5,045,086; 5,091,273; and 5,323.527. The separatormaterial may be any suitable dielectric material. The separator materialis almost always a mat made from thin glass fibers. Other materials havebeen used, such as polymer fiber mats, other ceramic fibers, rubbers,and various organic materials (such as certain papers). Fiberglass hasproven to be the best material. Several vendors are available from whichfiberglass separator material can be purchased such as Whatman andHollingsworth & Vose.

[0090] Another option for making spirally-wound lead acid cells withthin sheet electrodes is to form the electrodes in situ. Grooved orsurface irregular, unformed lead foil is wound with separator layersinto a cell coil and inserted into an open cell container. The sulfuricacid/nitric acid solution is then introduced into the cell. A current isthen run between the positive and negative electrodes. The electrodewhich is initially positive is activated by creation of a lead dioxideregion or regions into the lead. After the appropriate forming time haselapsed, then the current is reversed. The electrode comprising the leadoxide regions is reduced, such that the lead dioxide corrosion regionsare converted over to time to porous elemental lead. This electrode isused as the negative electrode in a battery cell. The opposite electrodeat the same time is oxidized, such that porous lead dioxide regions arecreated. The current is continuously passed, until the oppositeelectrode is fully electrochemically transformed into a positiveelectrode comprised of porous lead dioxide regions.

[0091] The spirally-wound batteries of the invention offer power storagecapacities (A·hr) which are close to or comparable to commerciallyavailable spirally-wound batteries. At the same time, the discharge andrecharge capabilities significantly exceed those of conventionalbatteries. Additionally, the cycle life of the batteries madeaccordingly to the present invention materially exceeds those of priorbatteries.

[0092] Nitric acid is preferably used as the lead-solubilizing agent inthe sulfuric acid electrolyte. Nitric acid has the advantage (over otherlead-solubilizing salts, such as the percholate species) of, after use,gradually decomposing to harmless byproducts during the formation.Rinsing is not required. The amount of nitric acid that is added to thecell initially can be metered such that enough (and typically onlyenough) nitrate is present to form porous layers on both electrodes ofthe desired depth. When the nitrate concentration drops low enough, thenfurther development of the porous lead dioxide region is inhibited.

[0093] The electrode forming process of the present invention minimizesproduction cost, both in terms of electrical power consumption and time.Capital outlay is not high. The production time is approximatelyeighteen hours less than is required to make the pasted electrodes. Lessthan 2 kW·hr of electricity will be required to form the electrodes fora single (12V) module. The manufacturing footprint required for thepresent formation process is believed not significantly larger than thepresent pasted electrode processes. Accordingly, practice of the presentinvention will result in a robust, high power density battery which ismanufacturable at low cost.

[0094] Silver oxide and zinc thin sheet electrodes with high and lowsurface irregularities are also of value in silver/zinc batteries.Silver/zinc batteries are commonly used by the U.S. Navy and otherdefense agencies, for energy storage where high energy density and powerdensity are important, and cost is not a factor. Silver/zinc batteriescan be built dry, and activated (i.e. filled with electrolyte)immediately prior to use. Sub-second fill times are sometimes important.This is often difficult with pasted silver oxide electrodes, due to thelong diffusion path of the electrolyte into the interior of the thick,porous electrodes. With thin, corrugated silver oxide and zinc sheetelectrodes, rapid filling is readily accomplished. Electrolyte isintroduced at one end of the thin sheet electrodes, and it then coursesvery rapidly along the grooves of the corrugations in the thin sheetelectrode. Furthermore, the grooves or low surface regions can functionas mini-reservoirs for retention of immediately accessible electrolyte.

[0095] The silver-zinc batteries, as with the lead-acid batteries, canbe either spirally-wound or bipolar. Each arrangement has advantages.The zinc is substituted for the lead-acid negative material (porouslead), and the silver oxide is submitted for the positive material (leaddioxide). The arrangement is otherwise essentially the same. Differentseparator materials are usually used (principally woven polypropylene orcellulose), although a fiberglass separator can be used for primary(non-rechargeable) batteries, used primarily by the military.

[0096] The process overtones of the invention differs from thetraditional Planté process, due in large part, to implementation withthe microthin sheet technology described above, to use of nitric acidwith thin sheet electrodes and to reduction in cost and powerrequirements. The known Planté manufacturing process is limited to thickelectrodes, which have unduly limited capabilities. The known Plantéprocess is considered costly relative to pasted electrodes production,particularly in terms of power and manpower requirements. In the knownprocess, electrodes are made by placing thick flat lead sheets informing tank containing sulfuric acid and, most commonly, potassiumperchlorate. The electrodes are electrochemically oxidized for 24 to 36hours, resulting in a porous lead dioxide film on the surface of thelead. The current may be reversed, to reduce the lead dioxide to porouslead metal. Two electrodes are not simultaneously formed. The potassiumperchlorate must be laboriously and repeatedly flushed or rinsed fromthe electrode pores and dried. The solution tank is then charged withsulfuric acid, without potassium perchlorate, for 24 to 72 hours priorto use. The time-intensive removal of potassium perchlorate prior toplacing electrodes in the final cell is essential, so that theperchlorate does not continue to corrode the underlying electrodesupport material. The perchlorate ion is difficult to destroyelectrochemically (its decomposition potential is around 4V relative tolead metal).

[0097] In contrast to the known Planté process, the present inventioncomprises a process including several key improvements to provide avastly superior product, to minimize cost and time, and to improvereliability. Use of nitric acid and elimination of potassium perchlorateas the lead solubilizing agent in the formation of microthin electrodes.Nitric acid has been found to be significantly effective in forming theporous active material region of thin sheet electrodes. Removal from theelectrode pores of spent nitric acid is not necessary, as the ionthereof gradually decomposes into a harmless form. More specifically,residual nitrate ions are entirely decomposed after the first few hoursof the initial charging of the battery.

[0098] Shortening of the formation process is significant. It has beenfound that only 3 hours of formation is needed to develop the desiredstructure on the thin sheet electrodes. Use of nitric acid as theforming agent shortens the time needed to reduce the thin sheetelectrodes (to form porous elemental lead metal) after initial formationof lead dioxide. The time reduction is from 24-36 hours to 3 hours (dueto eliminating the need for flushing perchlorate from the pores of theelectrodes). The reduction step is done in the present process not toremove the forming agent, but to prepare the positive thin sheetelectrodes. For spirally-wound thin sheet electrodes, the electrodes aremore durable in the lead state than in the oxidized state.

[0099] Conservation of both space and power using a continuous orsemi-continuous production approach is a further benefit. For example,after initial formation, the resulting electrodes are preferably used intandem or as counter electrodes for joint formation of thin sheetpositive and negative electrodes. This reduces power and timerequirements dramatically.

[0100] The result is a formation process which is approximately 6-7hours long, and which is adaptable to automation. The electrical currentrequirements of the thin sheet electrode forming cost are approximately6 A·hr per A·hr of final (six cell) battery capacity. The electricalenergy cost of formation, per six-cell, 15 A·hr battery isconservatively less than 2 kW·hr. For comparison, this energy cost issignificantly less than the energy required to do final charging andconditioning of the existing pasted electrode batteries, after assemblybut prior to shipping.

[0101]FIG. 3 is a flow sheet comparison between one version of a spiralbattery process of the invention and the prior-art pasted electrodeprocess for making batteries. Both processes begin by preparation ofmaterials and components. In the case of the present process, thestarting material is lead foil of suitable purity, and substantiallyuniform thickness. The foil is then passed through automated rollers tomechanically form corrugations, i.e. an array of grooves and ridges.

[0102] For pasted electrodes, the important starting materials are thelead grid and constituents of the paste. The lead grid is made bypunching holes in a lead plate of suitable purity. Commerciallyavailable lead oxides, of acceptable purity and in paste form, areobtained from a suitable vendor. The purity standards make the costs ofsuch pastes very high.

[0103] The processes of preparing electrodes differ, as shown in FIG. 3.An expanded schematic diagram of the traditional Planté formation isshown in FIG. 4.

[0104] In contrast, pasted electrodes require approximately 24 hours toprepare. The paste is mixed, and then applied to the grid, with apasting paper being placed on both sides of each electrode. The cellelement is then wound and placed in a suitable container, such as amonoblock container.

[0105] For the pasted electrode process, the curing of the electrodes,which is subsequent to placing the cell elements in the container, isthe most energy and time-intensive step. An unsealed monoblock is placedin a high temperature oven, with controlled humidity, for approximately24 hours. During this time, water is removed, and chemical reactionsoccur in the electrodes which prepare them to accept a charge later inthe fabrication process.

[0106] After winding and curing, the processes will be essentially thesame. The thin sheet electrodes of the invention can be final charged in24-48 hours, as compared to 72 hours for pasted electrodes.

[0107] In summary, the energy required for production of the twodifferent batteries is comparable. The time required for makingbatteries using the present process is approximately 18 hours less thanthe present pasted electrode processes.

EXAMPLES

[0108] The following examples demonstrate the production of bipolarelectrodes and spirally-wound electrodes for lead-acid batteries. Theresulting battery in each case is particularly suitable for use in HEVs.Joint studies by the HEV program by Department of Energy and variousautomotive manufacturers have demonstrated that, while the existingbattery designs approach most requirements for HEVs, there is still aserious difficulty in meeting the requirements for peak discharge powerand regeneration power. The power limitations are even more pronouncedwhen considered for use in parallel-configured hybrid vehicles of FIG.2. These vehicles require a battery pack which is smaller in size, andyet can be both discharged and recharged at rates comparable to thosespecified for the series-configured hybrid of FIG. 1.

[0109] The limitations in power are not due to the fundamentalelectrochemistry of the battery systems, but instead are due to theconfigurations and constraints of prior batteries, particularly theelectrodes.

Example I Bipolar Battery

[0110] In general, a bipolar battery of this invention comprises bipolarelectrodes, with separator layers placed between electrodes which arelaid upon one another like a stack of pancakes. A bipolar electrode of athin, flat conductive material (such as a metal foil), with a positiveactive electrode material deposited on one face, and a negativeelectrode placed on the opposite face. A bipolar cell comprises thepositive electrode side of one bipolar electrode, the negative electrodeside of a second closely spaced bipolar electrode and the electrolytebetween the two. On the ends of the battery are placed single-sided(monopolar) electrodes. Each individual cell is normally sealed toprevent electrolyte leakage.

[0111] This example demonstrates the manufacture and performance ofbipolar electrodes made in accordance with the present invention. Forcomparison purposes, a conventional bipolar electrode is illustrated inFIG. 5. The bipolar electrodes of the invention can be discharged andrecharged at very high rates. The electrode configuration has beendeveloped to assure that electrode active material (lead dioxide orporous lead) is highly accessible both ionically and electronically.Prototype electrodes were made by cutting large numbers of smallparallel grooves and ridges or forming other high and low surfaceregions in thin lead sheets, and then electroforming the irregularregions of the thin lead sheets using the process described above, tocreate a surprisingly large and uniform amount of active material. SeeFIG. 6. The metal solubilizing agent comprises sulfuric and nitricacids. The resulting bipolar electrodes were then used to assemble abattery in using conventional techniques aside from the electrodes.

[0112] Prototype bipolar batteries using the present microthin sheettechnology were assembled and tested. These prototype batteries not onlyexceeded existing standards for electric vehicle discharge power, butmet the regeneration power requirements as well.

[0113] With reference to FIG. 6, bipolar plate 40 is shown, which platemerges with a core 42 of unreacted lead.

[0114] The unreacted lead core 42 is a thin sheet comprising asubstantially concealed base 44 contiguous with one surface of thebipolar plate 40. Core 42 also comprises concealed rectangularly shapedridges or ribs 46. Core 42 is essentially a backbone supporting theactive regions of the thin electrode. The porous active regions 48collectively are undulating and comprise a porous layer over the ribs orridges 46 and the grooves between the ribs or ridges 46. The porousactive regions 48 covers the entire surface of the core corrugations andis uniformly corroded.

[0115] While the corrugation may comprise ridges and grooves which arerectangular in cross sections, other cross-sectional shapes can be used.Cross-hatched patterns, stamped into the metal, can be used. Repeatingand non-repeating surface irregularities may be used.

Example II Spirally-Wound Battery

[0116] This example demonstrates the manufacturing viability andperformance characteristics of a spirally-wound battery made inaccordance with the present invention. This configuration of theinvention meets all of the power requirements of the HEVs both seriesand parallel-configured.

[0117] Electrodes were made by taking strips of corrugated lead sheetand electroforming the corrugated lead using a process embodying theprinciples of the invention. See FIG. 11. The electrodes were thensandwiched with strips of separator material, and the combinationspirally wound into a cylindrical shape. See FIG. 12. After placing theroll into a cylindrical container (FIG. 13) and making appropriateelectrical connection, electrolyte was placed in the cell and the cellwas sealed.

[0118] The lead sheets were given high and low surface irregularities.Lead foil may be passed through rollers with small parallel ridges intheir surfaces to create corrugations by forming grooves in the leadfoil. Alternately, the lead foil may be stamped with a die defining thedesired surface irregularities, or engraved, or scratched or scored tocreate low and high regions.

[0119] For this example, thin lead sheets were scored by scratchingusing emery paper to create small irregular grooves and ridges. Thisless preferred procedure was expected to produce the cells having alower capacity than thin sheets carefully die pressed, grooved, orengraved. Lead foils of 0.010 and 0.016 inch thickness were used.Formation of the electrodes by the above-described process was carriedout in polypropylene tanks approximately 30 inches long, 8 inches tall,and six inches wide.

[0120] Two layers of 0.004 inch separator from Hollingsworth and Vose(Hovosorb II™) were used between the electrodes, in the manner shown inFIG. 11. Sulfuric acid of 5M concentration (1.28 g/cm³) was used as theelectrolyte.

[0121] Both positive and negative electrodes were completely formed ofthin sheets using the above-described process. After formation, theactive regions of each positive electrode was reduced to a porouselemental lead state. The electrode capacity was 14 C/cm³. Tabs 70 and72 were cut in the thin metal electrodes windings, in the manner shownin FIG. 14. More specifically, the thin sheet electrodes are formed withexcess bare metal (lead metal) at the top. After forming the activematerial, most of the bare metal at the top is cut away, except forplaced where tabs are needed. When the cell is wound, all of the tabsfor the positive electrode line up together on one side of the cell andthose for the negative line up on the other side. These tabs are thenlead welded together. Finally, intercell straps and posts are attached.The collection of four layer or cell wrap (FIG. 11) was rolled by handto the state shown in FIG. 12, and placed in a cylindrical cellcontainer 69. Terminals were made by inventing the cell wrap andimmersing the downwardly extending lead tabs 70 and 72 into two smallforms each filled with molten lead. One form of terminal is shown at 74,in FIG. 15. Two other terminal forms are shown in FIG. 16, i.e. bridgingterminals 76 and terminal posts 78. A monoblock is a battery. Severalindividual cells are placed in a single case or package. A monoblockusually consists of three cells, although six cells are also commonlyused. In a battery pack containing many cells (and therefore highvoltages), it is convenient to build the pack from several batteriescontaining the same number of cells. In a hybrid vehicle, a totalvoltage of around 360 V (at open circuit) is common. A pack is assembledfrom, for example,60 monoblocks, each operating at a nominal voltage of6V, containing three lead-acid cells of 2V each. Therefore, monoblockcontains three-cells are convenient.

[0122] Electrolyte at ambient temperature was injected into the cellwith a syringe. The cell was charged for 24 to 36 hours. The containerswere monoblock cases obtained from Optima Batteries, Inc., and of a sizeused for Optima's HEV programs.

[0123] These prototype cells were tested and found to have had acapacity of 3 to 5 A·hr. This capacity is below the capacity for cellsthat are constructed from lead foil grooved with rollers, which have acapacity of 12 to 13 A·hr, but nevertheless proved the viability of thethin sheet technology. This value was obtained by using the measuredvalue of specific electrode capacity (35 C/cm³), for non-spiralelectrodes using the desired roller grooved structure, multiplying bythe electrode area, and correcting for the under-used portions of thethin sheet electrodes (i.e. the outer and inner wraps).

[0124] Reference is now made to FIGS. 8 and 10 through 13, which areschematic diagrams illustrating the steps by which spirally woundbatteries of the invention. FIG. 8 illustrates an untreated thincorrugated sheet 50 from which a thin sheet electrode according to thepresent invention is formed. An electrochemically-treated electrode 52is shown in FIG. 10 which comprises an untreated metal support back bonecomprised of a base 54 and spaced ridges or ribs 56. Groove width priorto electroforming, was within the range of 2-20 mils. It should be notedthat during electroforming, the groove width decreases due to creationand expansion of porous active material on the walls of the ridges (i.e.the top and side of the ridges). The grooves often will close entirelywith oxidized material. This configuration with grooves which areentirely filled is also of considerable value, as the useful activematerial thickness of the electrode can be much greater thanconventional Planté electrodes.

[0125] Cutting low regions in the surface of lead, which are laterfilled due to oxidation of the lead ridges, results in a higher porosityat the back of the active material region. This happens because theactive material has somewhere to go as it forms. In other words, thevolume constraints are less severe when low regions are formed in thelead, so that higher porosity can develop deep and uniformly porousactive material regions. In addition to the improved microporosity, theuncorroded lead at the center of the lead ridges acts as a path forelectronic current flow during electrode operation. Thus, resistance toelectronic current is reduced in such electrodes, relative to activematerial regions which do not contain these thin ridges of lead. Thisimproved current collection is important. A major limitation of existinglead acid batteries, used in HEVs, is solid-phase voltage drop whichoccurs in the positive electrodes during high current use.

[0126] In FIG. 11, one positive electrochemically-formed thin sheetelectrode 60 and one negative electrochemically formed thin sheetelectrode 62, are aligned together with two separator sheets 64 and 66(FIG. 11) and tightly spirally wound into a coil 68 (FIG. 12). As wound,the coil comprises, seriatim, the positive electrode 60, the separatorsheet 64, the negative electrode 62, and separator sheet 66. The coil 68is then placed into a suitable cylindrical container 69 (FIG. 13).Electrical connections and posts and terminals are added, as is asuitable electrolyte as explained above.

[0127] Tests were made for discharge and recharge power on these opentop crudely-made cells. The data for one of the cells is shown in FIGS.17 and 18. The results were excellent and demonstrated the principles ofthis invention, notwithstanding deterioration of the cells due to thefact that the cells were open for an extended period while beingtransported to a testing facility. At the time of these tests, thecapacity had deteriorated to a capacity of 1 to 2 A·hr. A 200 Adischarge from the 1 to 2 A·hr cell was sustained for seconds at cellpotentials greater than 1.9 V. The recharge capabilities were also good.At approximately 50% state of charge, a 70 A recharge was done for 15seconds, during which the potential reached a maximum of 2.5 V. After 10seconds, the potential was 2.475 V.

[0128] Thus, a battery pack containing 172 cells (344 to 370 V nominalvoltage) would provide a pack voltage of 426 V. The regenerative powerimperative for a HEV is that the battery pack must be able to absorbapproximately 0.25 A·hr in ten seconds, at a total voltage of less than430 V. This prototype cell nearly achieved this value, absorbing 0.1 94A·hr during this time, despite having a total capacity of less than 2A·hr. A full recharge can be accomplished in less than a minute, ifnecessary. A healthy cell, such as one with a roller-grooved thin sheetelectrode, that is sealed, that is in a non-deteriorated condition, andthat has been subjected to good cell conditioning, will meet or exceedvarious HEV imperatives. The stack impedance for these cells wassignificantly less than that of existing batteries.

[0129] The present technology provides the improvements over the priorart, including but not necessarily limited to:

[0130] 1. Higher Discharge Power Sufficient to surpass programimperatives for peak discharge power and energy efficiency;

[0131] 2. Higher Recharge Power Sufficient to meet imperatives foreither the parallel or series-configured hybrid vehicles;

[0132] 3. Lower Heat Evolution;

[0133] 4. Ease of Manufacture Both the spiral cell manufacturing processis well established.

[0134] The Planté process is adopted to the electrodes proposed andmodified to lower costs and ease manufacturing.

[0135] 5. Low Cost -None of the processes involved require exotic andexpensive equipment.

[0136] 6. Batteries according to the present invention are expected tohave a long life. The thin sheet electrode eliminates grid corrosion, acommon source of failure of lead acid batteries. Batteries of thisinvention can last as long as twenty years, more than twice as long asother types of lead acid batteries.

[0137] While this invention has been described with reference to certainspecific embodiments and examples, it will be recognized by thoseskilled in the art that many variations are possible without departingfrom the scope and spirit of this invention, and that the invention, asdescribed by the claims, is intended to cover all changes andmodifications of the invention which do not depart from the spirit ofthe invention.

What is claimed and desired to be secured by Letters Patent is:
 1. Aspirally configurated high capacity battery cell comprising a positivespiral electrode layer and a separator layer interposed between thepositive electrode layer and a negative electrode layer, the positiveelectrode layer comprising a thin metal sheet comprised ofmicrocorrugations, the thin sheet of metal defining at least one surfaceregion comprising high microporosity.
 2. A battery cell according toclaim 1 wherein the thin metal sheet comprises lead, at least oneexposed surface of which is corroded.
 3. A battery according to claim 2wherein the corrosion first comprises a metal oxide and thereafterporous elemental metal.
 4. A battery cell according to claim 1 whereinthe thin sheet of metal comprises two surface regions comprising highmicroporosity.
 5. A battery cell according to claim 1 wherein the thinmetal sheet comprises silver, at least one exposed surface of which iscorroded.
 6. A battery cell according to claim 1 wherein themicrocorrugations comprise spaced grooves and further comprising amaterial, selected from the group consisting of electrolyte, gas,separator material or a combination thereof, placed and stored in thegrooves contiguous with the thin metal sheet.
 7. A battery cellaccording to claim 1 wherein the microcorrugations comprise spacedridges and valleys formed by forming grooves into the thin sheet.
 8. Abattery cell according to claim 1 wherein the microcorrugations comprisespaced ridges, each ridge comprising a corroded top surface portion andcorroded opposed side surface portions.
 9. A battery cell according toclaim 8 wherein the corroded top and sides comprise porous lead, whichtop and sides surround an and the interior conductive support region.10. A battery cell according to claim 1 wherein the microporosity isstable and between 5 and 95%.
 11. A battery cell according to claim 1wherein the battery cell comprises a lead acid battery cell.
 12. Abattery cell according to claim 1 wherein the battery cell comprises abipolar battery cell.
 13. A battery cell according to claim 1 whereinthe battery cell comprises a silver zinc battery cell.
 14. A batterycell according to claim 1 wherein the battery cell comprises an alkalinebattery cell.
 15. A battery according to claim 1 wherein at least oneexposed surface of the thin metal sheet at some point-in-time comprisesa metal oxide.
 16. A battery cell according to claim 15 wherein themetal oxide is formed using nitric acid in the presence of sulfuricacid.
 17. A battery cell according to claim 1 wherein both electrodescomprise thin metal foil.
 18. A battery cell according to claim 1further comprising a cylindrical housing surrounding the spiral array ofelectrode and separator layers.
 19. A battery cell according to claim 1wherein the positive and negative electrode layers are respectiveelectrically connected to positive and negative terminals.
 20. A batterycell according to claim 1 wherein the microcorrugations comprisesequentially arranged concave and convex grooves and ridges, each groovebeing generally trough-shaped in configuration.
 21. A battery cellaccording to claim 1 wherein the electrode layers and separator layersare spirally wound together.
 22. A battery cell according to claim 1wherein the sheet metal electrodes are cast.
 23. A battery cellaccording to claim 1 wherein the sheet metal electrodes are formed insitu.
 24. A battery cell according to claim 1 wherein themicrocorrugations are generally channel-shaped in configuration.
 25. Ina battery, a spirally-configurated electrode comprising a metal foilcomprised of corrugations comprising alternate grooves and ridges thesurfaces of which are electrochemically corroded to provide enhancedsurface porosity.
 26. In a battery, a spirally-wound metal foilelectrode according to claim 25 wherein the opposed sides and the top ofeach ridge are corroded and surround and conceal supportive andconductive material.
 27. In a battery, a spirally-wound electrode ofmetal foil according to claim 25 wherein each groove has a sizesufficient to serve as a reservoir for electrolyte.
 28. In a battery, aspirally-wound electrode of metal foil according to claim 25 wherein themetal is selected from the group consisting of lead, silver, zinc, andnickel.
 29. In a battery, a spirally-wound electrode of metal foilaccording to claim 25 wherein the size of the ridges are within therange of 2-20 mils wide and 2-20 mils high and the size of the groovesare within the range of 2-20 mils wide and 2-20 mils deep.
 30. In abattery, a spirally-wound electrode of metal foil according to claim 25wherein the depth of the corrosion is within the range of 0.01-30 mils.31. In a battery, a spirally-wound electrode of metal foil according toclaim 25 wherein the porosity is within the range of 5-90%.
 32. In abattery, a spirally-wound electrode of metal foil according to claim 25further comprising a bipolar conductive support in contact with themetal foil electrode.
 33. A method of providing a high capacityelectrode for a battery comprising the steps of corrugating andcorroding at least one side of a thin sheet of metal while greatlyincreasing the surface porosity at the at least one side followed bywrapping the thin metal sheet into a spiral configuration, theincreasing step comprising expanding of the metal being corroded intospaces between corrugations.
 34. A method according to claim 33 whereinthe thickness of the thin sheet is within the range of 4-62 mils.
 35. Amethod according to claim 33 wherein the corrugating step comprisescreating parallel grooves in the at least one side of the thin sheet.36. A method according to claim 35 wherein the width of each groove iswithin the range of 2-20 mils, the depth of each groove is within therange of 2-20 mils, and the spacing between consecutive grooves iswithin the range of 440 mils.
 37. A method according to claim 33 whereinthe corrugating step comprises creating microsized ridges and microsizedgrooves at both sides of the thin metal sheet.
 38. A method according toclaim 33 wherein the corroding step comprises exposure of at least oneside to a solubilizing agent for the metal comprising the thin sheetwhile applying electrical current to the thin metal sheet.
 39. A methodaccording to claim 33 wherein the one side is electrochemically surfacetreated to provide a high magnitude of microporosity.
 40. A methodaccording to claim 33 wherein the wrapping step comprises placing thethin corrugated corroded metal sheet contiguous with a separator layerand joining rolling the sheet, the separator layer, and anotherelectrode tightly together.
 41. A method according to claim 40 furthercomprising the step of placing the tightly rolled sheet and separatorlayer in a cylindrical container.
 42. A method according to claim 41further comprising the step of adding electrolyte to the interior of thecontainer using the corrugations as flow paths for the electrolyte. 43.A method according to claim 41 further comprising the step ofelectrically connecting the thin corrugated corroded metal sheet to aterminal comprising part of the container.
 44. A method according toclaim 33 further comprising placing a bipolar electrode contiguous withthe metal sheet.
 45. A method according to claim 33 wherein thecorroding step comprises creating lead oxide on lead using acid.
 46. Amethod according to claim 45 wherein the acid comprises nitric acid as alead solubilizing agent.
 47. A method according to claim 45 wherein thelead is simultaneously exposed to the acid and a selective flow ofelectrical current to create active lead dioxide material.
 48. A methodaccording to claim 47 wherein the flow of electrical current isselectively reversed to transform lead dioxide into porous elementallead.
 49. A method according to claim 33 wherein the corroding stepcomprises corroding the elevated crown and sides of each outwardcorrugation to a desired depth leaving a concealed untreated portion forsupport.
 50. In a method of making a lead acid battery, the steps ofproviding a thin sheet of lead having a thickness of 62 mils or less andcorroding at least one side of the thin sheet of lead using nitric acidas a solubilizing agent in lieu of potassium perchlorate in the presenceof sulfuric acid.
 51. In a method according to claim 50 furthercomprising the steps of leaving the nitric acid on the at least one sideof the thin lead sheet without rinsing after the corroding step followedby assembling the thin lead sheet into the lead acid battery.
 52. Amethod of high capacity use of a battery comprising the steps of causingelectrolyte to flow along grooves contained in a spirally-woundelectrode disposed within a battery container, storing electrolyte insaid grooves for immediate current accessibility and to reduce ionic andelectronic resistance, and cyclically, over a protracted time, placing ahigh load on the battery to deplete the stored energy and recharging thebattery substantially to essentially its prior energy level at ultrarapid rates.
 53. A method according to claim 52 when the rate of energydischarge is within the range of not greater than 20 C.
 54. A methodaccording to claim 52 when the rate of energy recharge is within therange of not greater than 20 C.
 55. In a battery, a bipolar conductor inelectrical communication with an electrode comprised of a thin metalsheet configurated to comprise a series of undulations comprised ofconcave and convex portions, the concave portions serving as receptaclesfor electrolyte.
 56. A high capacity battery comprising a corrugatedthin sheet of metal in electrical communication with a bipolarelectrode, grooves comprising the corrugations being disposed in thethin metal sheet to form receptors for electrolyte and ridges comprisingthe corrugations being disposed in the thin metal sheet defining surfaceregions comprised of highly porous corroded metal.
 57. A high capacitybattery according to claim 56 wherein at least one of the groovescomprise a rectangularly-shaped trough and at least one of the ridgescomprising a rectangularly-shaped crown.
 58. In a method of making abipolar battery, the steps of: corrugating and corroding at least oneside of a thin sheet of metal to greatly increase the surface porositythereof and placing the thin metal sheet in electrical communicationwith a bipolar electrode.
 59. A high capacity battery cell comprising apositive electrode comprising a thin metal sheet, a negative electrodecomprising a second thin metal sheet, a non-conductive separator layerinterposed between the positive and negative electrodes and electrolyte,each thin metal sheet comprising microporous irregularities comprisinghigh and low surface regions.
 60. A high capacity battery cellcomprising a positive electrode comprised of a thin metal sheet, anegative electrode, non-conductive separator material interposed betweenthe positive and negative electrodes, the thin metal sheet comprisingmicroporous irregularities comprising high and low surface regions. 61.A battery cell according to claim 60 wherein the negative electrodecomprises a pasted electrode.
 62. A high capacity battery cellcomprising a spirally-sandwiched array comprised of a spirally-disposedpositive electrode, a spirally-disposed negative electrode, a dielectricseparator contiguously between the positive and negative electrodes andelectrolyte, the positive electrode comprising a thin sheet of metalelectrochemically corroded on both sides to comprise enhanced porosity.63. A battery cell according to claim 62 further comprising anelectrical conductor spanning between the positive electrode and apositive terminal and between the negative electrode and a negativeterminal.
 64. A method of providing a high capacity electrode for abattery comprising the steps of corrugating and electrochemicallycorroding both sides of a thin sheet of metal materially increasingbi-surface porosity, accommodated by expansion into spaces betweencorrugations.
 65. A method of providing a high capacity electrode for abattery comprising the steps of electrochemically corroding both sidesof a thin sheet of metal materially increasing bi-surface porosity andwrapping the thin metal sheet into a spiral configuration.
 66. A methodof simultaneously forming both positive and negative battery cellelectrodes comprising the steps of placing thin metal electrodes in acontainer in the presence of nitric acid and driving current through thecontainer first in one direction and then in the opposite direction toelectrochemically form porous elemental metal and oxidized metal on thenegative and positive electrodes, respectively.